Add per-app flock locking around deploy, config change, rollback, new-app

Nothing previously serialized these against each other, so concurrent
invocations for the same app (a manual config change racing an
in-flight deploy, a double git push, a rollback mid-deploy) could
interleave snapshot/apply/restart/rollback sequences against the same
dataset and jail. The lock file lives under a new LocksDir, outside
any per-app ZFS dataset, since those datasets get rolled back on a
failed health check or a manual rollback.

1 files changed, 27 insertions, 1 deletions

diff --git a/cmd/skiff/main.go b/cmd/skiff/main.go
index 1c48681..7c9d505 100644
--- a/cmd/skiff/main.go
+++ b/cmd/skiff/main.go
@@ -16,6 +16,7 @@ import (
 	"skiff/internal/envfile"
 	"skiff/internal/jailmgr"
 	"skiff/internal/layout"
+	"skiff/internal/lock"
 	"skiff/internal/sh"
 	"skiff/internal/tmpl"
 	"skiff/internal/zfsutil"
@@ -65,7 +66,14 @@ func cmdDeploy(args []string) error {
 		return nil
 	}
 
-	return deploy.Run(context.Background(), os.Stdout, layout.Default(), *app, *newSHA)
+	cfg := layout.Default()
+	unlock, err := lock.Acquire(cfg.LockPath(*app))
+	if err != nil {
+		return fmt.Errorf("acquire app lock: %w", err)
+	}
+	defer unlock.Release()
+
+	return deploy.Run(context.Background(), os.Stdout, cfg, *app, *newSHA)
 }
 
 func cmdNewApp(args []string) error {
@@ -89,6 +97,12 @@ func cmdNewApp(args []string) error {
 	out := os.Stdout
 	cfg := layout.Default()
 
+	unlock, err := lock.Acquire(cfg.LockPath(*name))
+	if err != nil {
+		return fmt.Errorf("acquire app lock: %w", err)
+	}
+	defer unlock.Release()
+
 	fmt.Fprintf(out, "==> cloning %s@%s -> %s\n", cfg.BaseDataset, *baseSnapshot, cfg.AppDataset(*name))
 	if err := zfsutil.Clone(ctx, out, cfg.BaseDataset, *baseSnapshot, cfg.AppDataset(*name), cfg.JailRoot(*name)); err != nil {
 		return fmt.Errorf("clone base dataset: %w", err)
@@ -161,6 +175,12 @@ func cmdRollback(args []string) error {
 		return fmt.Errorf("--to is required (use --list to see snapshots)")
 	}
 
+	unlock, err := lock.Acquire(cfg.LockPath(*app))
+	if err != nil {
+		return fmt.Errorf("acquire app lock: %w", err)
+	}
+	defer unlock.Release()
+
 	if err := zfsutil.Rollback(ctx, os.Stdout, dataset, *to); err != nil {
 		return fmt.Errorf("rollback: %w", err)
 	}
@@ -275,6 +295,12 @@ func applyConfigChange(app string, mutate func(map[string]string) error) error {
 		return fmt.Errorf("app %q not found: %w", app, err)
 	}
 
+	unlock, err := lock.Acquire(cfg.LockPath(app))
+	if err != nil {
+		return fmt.Errorf("acquire app lock: %w", err)
+	}
+	defer unlock.Release()
+
 	kv, err := envfile.Load(cfg.EnvPath(app))
 	if err != nil {
 		return fmt.Errorf("load config: %w", err)